The crime bill that President Bush has made a top priority is being dismissed as a rehash of old proposals. But on at least one point - guns and the exclusionary rule - the administration is championing a new idea.

The exclusionary rule, as crime buffs know, is what keeps out of court evidence obtained illegally.First applied by the Supreme Court in 1914, the rule deters overzealous police who would trample the Constitution's ban on unreasonable searches and seizures.

The trouble is, the rule also hobbles honest police.

Sometimes the illegality resides in a point so fine that officers cannot reasonably know their actions are out of bounds.

All the same, valid evidence is withheld from the jury. Criminals win, society loses and police conduct is largely unaffected.

The Supreme Court cleared up many such problems by creating the "good faith exception" in 1984: Evidence is admissible in court if the officers who gathered it reasonably believed their search warrant was legal.

The administration again proposes, as it did last year, to extend the good faith exception to cases where searches require no warrant - searches incident to arrest, for example, or those to which a person consents.

But here's the innovation: A whole new exception to the exclusionary rule would also be created, specifically for guns.

Firearms seized by federal officers could always be used as evidence in federal prosecutions for crimes of violence, serious drug offenses or illegal possession of firearms.

And any misconduct by the agents who seized the guns would be separately punished.

The attorney general would promulgate a series of penalties for errant law enforcement officers, including suspension and dismissal. The Department of Justice would oversee the system.

Skeptics will predict token penalties and lax enforcement - with Fourth Amendment protections accordingly weakened. If that were the result, this experiment should be repealed.

But why give its obvious merits short shrift? The new approach would disencumber criminal trials of tangential questions about police conduct.

In precisely the cases of which Americans are most weary - those involving violence and drugs - it would permit juries to learn that guns had been involved.

Shouldn't it be possible to discipline incompetent police without distorting trials and rewarding criminals?